Compensated thermal motor



y 1949. R. GJOLSON 2,468,996

COMPENSATED THERMAL MOTOR Filed April 14, 1947 Ju /ww aiwwe gazwag Patented May 3, 1949 COMPENSATED THERMAL MOTOR Ray G.. Olson, Glenview, 111., assignor to The Magnavox Company, Fort Wayne, Ind, a corporation of Delaware 1 Application April 14, 1947, Serial No. 7411240 7 Claims.

The present invention relates to an arrangement for automatically eliminating the undesired effects of voltage or heating-current variations in electric heaters, specifically in the heating elements of bimetallic devices.

In the copending patent application of John C. Koonz, entitled Bimetallic variable speed timer, Serial No. 733,441, filed in the United States Patent Office on March 8, 1947, and assigned to the same assignee as the present invention and application, there is shown a timer comprising a bimetallic device, the periodic mechanical pulsations of which actuate a, ratchet-and-pawl mechanism controlling cam switches or the like. If the heating current supply for such a device, or any bimetallic device for performing a timing function, is not regulated, then it is desirable to provide some arrangement for eliminating the undesired efiects of heating-current variations in the heating element or elements of the bimetallic device. Undesired average current increases tend to speed up the operation of the timer shown in that application, for example. Conversely, undesired decreases produce a retarding efiect.

It is the primary object of the present invention to provide a compensator which automatically prevents, diminishes or compensates for the an desired effects of heating-current variations in the heating elements of bimetallic devices.

Other advantages and capabilities of the invention will become apparent as the following description proceeds. In the drawings there is shown a bimetallic variable speed timer including a prefered form of compensating device in accordance with the invention. Fig. 1 is a schematic and perspective view thereof; and Figs. 2, 3 and 4 are sectional views taken on lines 2-2 of Fig. 1,

3-3 of Fig. 2 and 4-4 of Fig. 2, respectively.

For a detailed description of the timer per see, reference is made to the above-mentioned copending application of John C. Koonz. It consists essentially of a bimetallic impulsing device comprising element 5 I, a ratchet-and-pawl mech" anism i3 actuated by the impulsing device, and a plurality of cam switches l4, l5, l5 controlled by cams ll, l8, is rotatably carried by a shaft 26. The impulser is mounted in slots on posts 2 I, 22, secured to insulating base 23. The cam switches are sequentially closed as shaft rotates. The shaft is intermittently turned by pawl 24. successively engaging teeth on ratchet wheel 25. The pawl is pivotally mounted on a bifurcated pawl mounting 26, secured to the bimetallic impulser H. As the impulser element is heated, it snaps from the normal position shown in full lines to ill 2 that shown in dashed lines. in Fig. 2, pushing pawl 24 upwardly and turning wheel 25 by one tooth. As the impulser element cools, it snaps back to its normal position,

A dished member H, initially and integrally formed of layers of suitable thermo-acting dissimilar materials and generally referred to as a bimetallic element H is provided.

The result is that the switches l4, l5, it are closed at intervals dependent on the rate of generation of impulses by bimetallic element H. This, in turn, depends on the voltage applied to the heater. It will be seen that best operation is obtained when the voltage supply is stabilized or regulated.

The impulser is so arranged that when the element ll, snaps from the full-line position to the dashed-line position the heater is disconnected, so that the element then cools.

It will be seen that the desired periodicity of the action of impulser ll would be adversely afiected by undesired heating-current variations. In accordance with the invention there is provided a voltage compensating device for preventing such undesired efiects. It comprises means responsive to undesired current increases for automatically increasing the distance between the bimetallic element ii and the heating elements 29, so during the heating cycle. This means is also responsive to undesired current decreases for automatically decreasing the distance between the bimetallic element H and the heating elements 2Q, during the heating cycle.

Specifically, heating elements 29 and 3B are mounted on insulation strips 3| and 32, which are secured by rivets 33, 34 and washers 31, 38 to a bimetallic strip 35, also initially and integrally formed of suitable thermoacting dissimilar materials such as brass and stainless steel, for example. When element is heated element 35 bends from the normal section illustrated in full lines in Fig. 2 to some more curved section illustrated in dashed lines. The amount of this increase in curvature depends on the average amount of current flowing in heater 29, 30, i. e on the heat generated by the heater.

When element 35, disposed in convex relation to element I i, bends away from a normal section, the distance between heater 29, 30 and bimetallic element I i is increased by an amount functionally related to the excess of the amount of current flowing in heater 29, 30 over the normal amount flowing when the normal section is maintained.

Conversely, when the amount of current flowing in the heater is below the normal value, bi-

metallic strip 35 becomes less concave than normal relative to bimetallic element i! and the distance between the heater and bimetallic element ii is decreased.

The result is that undesired voltage or current increments, which cause more heat to be generated by heater 29, 30, also cause the heater to be moved away from element ll, thereby decreasing the amount of that heat actually applied to element i 8, whereby the undesired effects of voltage or current increments are neutralized, compensated for or minimized. Conversely, undesired current or voltage decreases, which cause less heat to be generated by heater 29, also cause the heater to be moved toward element I I, whereby increasing the amount of that heat actually applied to element H, whereby the undesired efiects of voltage or current decreases are neutralized. compensated for or minimized.

It will be understood that my invention is not limited to the particular application shown but is of general utility wherever it is desired to neutralize or compensate for undesired voltage or current deviations in electric heaters.

Integral screw-threaded extension 39 of pawlmounting 28 projects through an aperture in bimetallic device ii, a washer 40, washers 4i and 42 to a lock nut 43. The displaceable portions of element ll, pawl 24, pawl-mounting 28, extension 39, compensator 35, washers ll, 42 and lock nut 43 are thus rigidly secured in assembly whereby they move upwardly and downwardly in unison. Insulating strips 32 and ll overlie strip 35, whereby heater elements 29, I0 are mounted for unobstructed movement toward or away from element H.

The electrical circuit for heater 2!, I0 begins at binding post 45 on base 21 and proceeds through flexible lead N, terminal 41 on strip 32, heater element or resistor 30, conductor 48, heater element or resistor 29, terminal 49 on strip 32, flexible lead 50, extension 3!, lock nut 43, fixed contact II, and binding post 52 on base 2!. Posts 45 and 52 are coupled to a suitable source of heating current (not shown).

When element ll snaps from the full-line positicn illustrated in Fig. 2 to the dashed-line position, nut 43 is separated from contact ll, breaking the electrical circuit and permitting elements I I and 35 to cool. when element H cools itsnaps back to its normal position, whereby the electrical circuit is again closed at 0, II and the cycle is repeated. When strip ll cools it bends back to its normal position.

Thus,,there is provided a simple, inexpensive, reliable arrangement for automatically eliminating the undesired effects of voltage or heating current variations in electrical heaters. This device is of particular utility when the heater is employed to furnish energy to a bimetallic impulsing device or timer.

While there have been shown and described what are at present; considered to be the preferred embodiments of the present invention, it will be obvious to those skilled in the art that various modifications and substitutions of equivalents may be made without departing from the teachings of the invention and the proper scope thereo! and it is accordingly intended in the appended claims to cover all such changes and modifications as fall within the true scope of the invention and outside of the scope of the prior art.

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Having thus described my invention, I claim:

1. A thermally actuated timing device comprising a dish-shaped snap-impulse bimetallic operating member supported at its outer edges and adapted when heated to snap from a normal position to an inverted position and when cooled to return to normal position; a shiitable fitting at the center of said operating member and a compensating member mounted on said fitting; the compensating member comprising an auxiliary bimetallic member strip adapted to flex in one plane only and secured to the fitting at the midpoint of the strip whereby the opposite ends of the strip are unsupported and adapted to fiex gradually and progressively away from the operating member in response to heat; an electrical heating unit extending between the unsupported ends of the bimetallic strip, and a pair of breaker contacts responsive to the movement of the operating member to break the circuit through the electrical heating unit.

2. A thermally actuated timing device comprising a dish-shaped snap-impulse bimetallic operating member supported at its outer edges and adapted when heated to snap from a normal position to an inverted position and when cooled to return to normal position; a shlftable fitting at the center of said operating member and a compensating member mounted on said fitting; the compensating member comprising an auxiliary bimetallic member strip adapted to fiex in one plane only and secured to the fitting at the midpoint of the strip whereby the opposite ends of the strip are unsupported and adapted to flex gradually and progressively away from the operating member in response to heat; and an electrical heating unit extending between the unsupported ends of the bimetallic strip.

3. A thermally actuated timing device comprising a, dish-shaped snap-impulse bimetallic operating member supported at its outer edges and adapted when heated to snap from a normal position to an inverted position and when cooled to return to normal position; a shiitable fitting at the center oisaid operating member and a compensating member mounted on said fitting; the compensating member comprising an auxiliary bimetallic strip adapted to fiex in one plane only and secured to the fitting whereby the strip is adapted to fiex gradually and progressively away from the operating member in response to heat; and an electrical heating unit supported by said bimetallic strip.

4. A thermally actuated timing device comprising a bimetallic operating member adapted when heated to move from a normal position and when cooled to return to normal position; a shiitable fitting carried by said bimetallic operating member and a compensating member mounted on said fitting; the compensating member comprising an auxiliary bimetallic member secured to the fitting adapted to flex gradually and progressively away from the operating member in response to heat; and an electrical heating unit supported by and movable with the bimetallic compensating member.

5. In a thermally actuated timing device including a bimetallic operating element, the combination of a voltage compensating device comprising a second bimetallic element oppositely oriented to the operating element but adjacent to, directly supported by, and shiftable with the operating element; together with an electrical heating unit for the operating element directly supported on and carried by said second bimetalsponse to movement of said second bimetallic ele-,

ment.

7. In a thermally actuated timing device including a bimetallic operating element, the combination of a voltage compensating device comprising a second bimetallic element oppositely oriented to the operating element, together with an electrical heating unit shiftable with the second bimetallic operating element, whereby the g0 heating unit moves away from the operating element inresponse to increasing heater temperature and toward said operating element in response to decreasing heater temperature, whereby the heating ,unit and operating element are maintained in variable spaced relationship inversely proportional to temperature.

RAY 2G. OLSON.

REFERENCES, crrn The following references are of record in the file of this patent:.

, UNITED STATES PATENTS Number Name Date 1,649,506 Brewer Nov. 15, 1927 1,987,717 Smith Jan. 15, 1935 2,002,467 Blodgett May 21, 1935 2,285,720 Joy June 9, 1942 2,347,385 Wright et a] Apr. 25, 1944 2,270,961 McCabe Jan. 27, 1942 

